Steam generating unit



June 23, 1970 A. H. RAWDON 3,516,391

STEAM GENERATING UNIT Filed June 20, 1968 ALBERT RAWDON INVENTO FIG. 2

3,516,391 STEAM GENERATING UNIT Albert H. Rawdon, Shrewsbury, Mass., assignor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Filed June 20, 1968, Ser. No. 738,631 Int. Cl. F221) 37/32 US. Cl. 122-491 7 Claims ABSTRACT OF THE DISCLOSURE A steanrand-water drum employing a scroll-type separator having scroll wall means defining plural parallel flow paths and slot defining means such as peel-off plates adjacent the outer wall of each path to separate the liquids thrown against the outer wall.

BACKGROUND OF THE INVENTION In the art of generating steam, one of the outstanding problems is that of obtaining pure steam. It is the usual practice to separate the steam from the boiler water in a separating vessel known as a steam-and-water drum, the water falling to the bottom of the drum for recirculation through the boiler and the steam rising to the top eventually to progress to a turbine. In most cases, however, after leaving the drum, this steam is first subjected to further heating to superheat it. Whether the steam flows directly to the turbine from the drum, or is subjected to a superheating step, it is important that no particles of water pass out of the drum with the steam. It is also important that certain chemicals dissolved in the water droplets do not leave the drum with the steam because this would result in a coating of the superheater or turbine surfaces and destroy their effectiveness. Many schemes have been provided in the past for purifying steam in the drum, but they have been as a rule quite expensive and have been economically unfeasible for boilers of small or intermediate size where cost is an important consideration. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a steam generating unit containing a steam separating apparatus which is extremely effective in operation and yet is low in cost.

Another object of this invention is the provision of a steam generating unit containing steam cleaning apparatus which is simple and uncomplicated in construction and which is relatively free of maintenance problems.

A further object of the present invention is the provision of a steam generating unit having steam cleaning equipment which may be readily installed and replaced through a manhole in the steam-and-water drum.

It is another object of the instant invention to provide a steam cleaning apparatus which is simple and uncomplicated in concept and which will not be rendered inoperative by salt deposits or the like.

A still further object of the invention is the provision of a steam separator which is inexpensive to manufacture and which is capable of a long life of useful service with a minimum of care.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, the present invention consists of a steam generating unit having a steam-and-water drum of generally elongated cylindrical form, having a steam sepanited States Patent rator housing of elongated tubular form lying in the drum with its axis parallel to the axis of the drum, having an inner tube which is of substantially less diameter than the housing lying coaxially thereof, having a scroll wall extending generally coaxially of the tube midway between the tube and the housing to provide two steam paths, and having slots located at the outer periphery of each path to pick up water from the steam flow for disposal.

More specifically, entrances are provided into the housing at selected positions along its length for fiow of steam into the two paths and exits are provided from the housing at positions between the said selected positions for the flow of steam out of the two paths. A peel-off p ate extends upstream from the downstream edge of each slot in the upstream direction with its upstream edge spaced from but close to the inner surface of the housing or the scroll wall, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 shows a portion of a steam generating unit embodying the principles of the present invention, and

FIG. 2 shows an enlarged sectional view of a portion of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the steam generating unit, indicated generally by the reference numeral 10, is shown as consisting of a steam-and-water drum 11 which is of generally elongated form and has connected to its bottom portion steam release tubes 12 and downcomer tubes 13. A boiler feed pipe 14 lies in the bottom of the boiler to maintain a level 15 of water in the bottom of the drum. A continuous blowdown pipe 16 and a chemical feed pipe 17 are also located in the bottom of the drum. A baffle 18 extends angularly across the bottom of the drum to trap the steam arriving in the steam release tubes 12 and direct them to one side of the drum. The upper edge of this bafile extends above the water level 15 and beside this upper edge is located a primary separator 19 consisting of paral el perforated plates extending longitudinally of the drum and capped by a horizontal plate 21. At the left-hand edge of the plate 21 is located a housing 22 which is of an elongated tubular form which lies in the drum with its axis parallel to the axis of the drum, the housing having closed ends. An inner tube 23 of tubular form of substantially less diameter than the diameter of the housing 22 lies coaxially of the housing. A scroll wall 24 extends generally coaxially of the tube midway between the tube and the housing 22 to divide the space between them into two steam paths 25 and 26. The slot 27 is located at the outer periphery of the path 26 and extends through the scroll wall 24, while a similar slot 28 extends through the housing 22, these slots being adapted to pick up water from the steam flow for disposal.

The slot 27 in the scroll wall 24 is connected by drainage tube 29 which extend radially across the space between the scroll Wall and the housing. These drainage tubes extend through the housing 22 into a collection trough 31 which, in turn, is connected by a pipe 32 to the lower portion of the drum where its lower end lies under the water level 15. The slot 28 in the housing 22 also opens into the collection trough 31 and releases liquid thereto.

Entrances 33 are provided into the housing 22 at selected positions along its length for the flow of steam into the paths 25 and 26. At the same time, similar exits 34 are provided from the housing 22 at positions which alternate with and lie between the said selected positions for the flow of steam out of the two paths into the steam off-take pipe 35 of the drum. A peel-off plate 36 extends upstream from the downstream edge of the slot 27 so that its upstream edge is spaced from but close to the inner surface of the scroll wall 24. A similar peel-01f plate 37 extends from the downstream edge of the slot 28 in the housing 22 to an upstream position slightly spaced from the inner surface of the housing.

The operation of the invention will now be readily understood in vie-w of the above description. The steam from the steam release tubes 12 enters the steam-andwater drum 11, flows along the baflle 18 into the chamber defined by the water level 15, the separator 19, and the upper plate 21. The steam then flows through the separator 19 and into the housing 22 through the entrances 33. The steam divides itself between the path 25 and the path 26 and flows in a circular path, eventually reaching the peel-off plates 36 and 37. The water, being heavier than the steam, is thrown outwardly by centrifugal force in each path and enters the space between the peel-off plates and the surface of the scroll wall 24 or the housing 22. The water which flows under the peel-off plate 36 goes through the slot 27, through the drainage pipes 29 into the collection trough 31. Similarly, the water entering between the peel-off plate 37 and the inner surface of the housing 22 goes through the slot 28 into the collection trough 31. The water from both slots then flows downwardly through the pipe 32 to the water in the bottom of the drum. The steam, however, continues onwardly and goes out through the exits 34 into the space above the plate 21 and then into the pipe 35 to superheat or to the turbine.

FIG. 2 shows the construction that is used at the downstream end of the plate 37. An L-shaped catcher 38 overlies the end of the plate and guides droplets into a slot 39 leading to the slot 28. When the steam flows past the leading edge of the plate 37, the aerodynamic flow is divided between the two sides of the plate. The portion that fiows between the plate and the housing travels directly to the slot 28. The portion that passes between the plate 37 and the scroll 24 is thrown toward the plate 37 and, eventually, the heavier portions and droplets are gathered by the catcher 38. The leading edge of the catcher also divides the fiow, the heavier portion flowing into the slot 39 and the remainder going through the passages 34. A similar construction is used at the downstream edge of the peel-off plate 36. In general, then, the present invention divides the total steam fiow into two parts and, then, subjects each part to a double catcher action.

The present construction has proved to be extremely practical because its resistance to steam flow seems to be about the same, irrespective of the amount of steam which flows through it, i.e., irrespective of the load on the boiler. It results in a high purity steam despite the fact that a great deal of steam is passed through the separator per unit length; it is compact and capable of being introduced through a manhole at the end of the steam-and-water drum.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed,

The invention having been thus described, What is claimed as new and desired to secure by Letters Patent is:

1. A steam generating unit, comprising (a) a steam-and-water drum of generally elongated cylindrical form,

(b) a steam separator housing of elongated tubular form lying in the drum with its axial parallel to the axis of the drum,

(0) an inner tube which is of substantially less diameter than the housing lying coaxially thereof,

(d) a scroll wall extending generally coaxially of the tube midway between the tube and the housing to provide plural parallel steam paths, and

(e) means defining slots located adjacent the outer periphery of each path to pick up water from the steam flow for disposal.

2. A steam generating unit as recited in claim 1, wherein entrances are provided into the housing at selected positions along its length for flow of steam into the two paths and wherein exits are provided from the housing at positions alternating with the said selected positions for the flow of steam out of the two paths.

3. A steam generating unit as recited in claim 2, wherein the slot in the scroll was is connected to drainage tubes which extends radially across the space between the scroll wall and the housing.

4. A steam generating unit as recited in claim 3, wherein a collection trough underlies the housing and receives water from the slot in the housing and from the drainage tubes and wherein a pipe extends from the trough to the lower part of the steam-and-water drum.

5. A steam generating unit as recited in claim 2, wherein the slot defining means includes a peel-off plate extending along each path and lying closely adjacent the outer periphery thereof.

6. A steam generating unit as recited in claim 5, wherein the slot defining means further includes a catcher plate extending from a position along said path beyond said peel-off plate to a position extending over the peeloff plate.

7. A steam generating unit as recited in claim 5, wherein a catcher is associated with the downstream edge of each peel-off plate, the catcher having a radial portion extending from the downstream edge of its respective slot and spaced from the downstream end of the plate to define a secondary slot, the catcher also having a flange at the inner part of the radial portion, which flange extends backwardly coextensive with and parallel to the plate.

References Cited UNITED STATES PATENTS 1 1,950,285 3/1934 Battle et al. s5 397 2,221,385 11/1940 Rogers 461 3,189,007 6/1965 Kuhner 55 397 XR FOREIGN PATENTS 890,653 9/1953 Germany.

KENNETH W. SPRAGUE, Primary Examiner U.S. Cl. X.R.

mg UNITED STATE: PATENT OFFICE CERTIFICATE 2F CORRECTION Patent No. 3 516 391 D ted June 2 3 1970 Inventofls) Albert H. Rawdon It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I" fi Column 2, line 60, the word "tube" should be --tubes;

Column 4, line 7, the word "axial" should be --axis-;

line 24, the word "was" should be wal1--;

SIGNED ANA: T will W201!!!) ISEAL) Attest:

Edward M.Flewher, In Gilli-Alli]. sag. n;

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